Study of Latinos: Nutrition & Physical Activity Assessment Study (SOLNAS) Under-reporting of energy intake and expenditure by self-report obscures the relationship between diet, physical activity and health outcomes. Studies using biomarkers have had a small number of Hispanics limiting ability to assess the extent of measurement error and its correlates in the diverse US Hispanic population. This proposed study will be conducted in the Hispanic Community Health Study-Study of Latinos (HCHS-SOL), an NIH-NHLBI funded study of Hispanics/Latinos in the Bronx, Miami, Chicago and San Diego. Disparate rates of disease in the Hispanic population will be addressed in the parent study and the biomarker data derived from the proposed study can improve the precision of dietary and physical activity assessments related to differences found in disease rates among Hispanic/Latino sub-groups. The biomarker data from the proposed study will have the potential to calibrate nutrient and physical activity self-report data to increase reliability of disease association analyses. The principal aims of the proposed study are to: 1) To compare energy and protein data from the 24 hr dietary recall to the gold standard biomarkers Doubly Labeled Water (DLW) for energy and urinary nitrogen for protein in the HCHS-SOL study; to compare physical activity energy expenditure data from study questionnaires to the Actical (an accelerometer for measuring physical activity), DLW and indirect calorimetry. 2) To contrast measurement error properties of: (i) the 24 hr dietary recall; (ii) the 24 hr dietary recall with the addition of the Food Propensity Questionnaire (FPQ) (iii) SOL Physical Activity Questionnaire; (iv) the Tufts University Puerto Rican/Dominican Food Frequency Questionnaire. (Bronx only); 3)To use the fitted measurement error model to produce calibrated intake and physical activity measures on the full HCHS-SOL cohort for use in analyses of clinical outcomes. PUBLIC HEALTH RELEVANCE: Under-reporting of energy intake and expenditure by self-report obscures the relationship between diet, physical activity and health outcomes. Studies using biomarkers have had a small number of Hispanics limiting ability to assess the extent of measurement error and its correlates in the diverse US Hispanic population. This proposed study will be conducted in the Hispanic Community Health Study-Study of Latinos (HCHS-SOL), an NIH-NHLBI funded study of Hispanics/Latinos in the Bronx, Miami, Chicago and San Diego. Disparate rates of disease in the Hispanic population will be addressed in the parent study and the biomarker data derived from the proposed study can improve the precision of dietary and physical activity assessments related to differences found in disease rates among Hispanic/Latino sub-groups. The biomarker data from the proposed study will have the potential to calibrate nutrient and physical activity self-report data to increase reliability of disease association analyses.